Patient interfaces

ABSTRACT

The present invention relates to a device for delivering a supply of gases to a patient. The device includes a patient interface and connecting member. The connecting member is preferably a L-shaped swiveled connector that is capable of being fixed into one of two positions, a first position where the connector is freely rotatable within the patient interface, and a second position where an interference between the interface and connector prevents the free rotation of the connector within the patient interface, The present invention further relates to a connector that has outlet means, which includes at least one outlet vent and a funnel, which in use directs and passes a substantial portion gases expired from the patient through the outlet vent or vents.

INCORPORATION BY REFERENCE TO PRIORITY APPLICATIONS

All applications for which a foreign or domestic priority claim is identified in the Application Data Sheet as filed with the present application are hereby incorporated by reference under 37 C.F.R. § 1.57.

BACKGROUND OF THE INVENTION Field of the Invention

This invention relates to patient interfaces, particularly though not solely for use in providing Continuous Positive Airway Pressure (CPAP) therapy or positive pressure ventilation to patients suffering from obstructive sleep apnoea (OSA).

Summary of the Related Art

In the art of respiration devices, there are well known a variety of respiratory masks which cover the nose and/or mouth of a human user in order to provide a continuous seal around the nasal and/or oral areas of the face such that gas may be provided at positive pressure within the mask for consumption by the user. The uses for such masks range from high altitude breathing (i.e., aviation applications) to mining and fire fighting applications, to various medical diagnostic and therapeutic applications.

One requisite of such respiratory masks has been that they provide an effective seal against the patient's face to prevent leakage of the gas being supplied. Commonly, in prior mask configurations, a good mask-to-face seal has been attained in many instances only with considerable discomfort for the user. This problem is most crucial in those applications, especially medical applications, which require the user to wear such a mask continuously for hours or perhaps even days. In such situations, the user will not tolerate the mask for long durations and optimum therapeutic or diagnostic objectives thus will not be achieved, or will be achieved with great difficulty and considerable user discomfort.

Where such masks are used in respiratory therapy, in particular treatment of obstructive sleep apnoea (OSA) using continuous positive airway pressure (CPAP) therapy, there is generally provided in the art a vent for washout of the bias flow or expired gases to the atmosphere. Such a vent may be provided for example, as part of the mask, or in the case of some respirators where a further conduit carries the expiratory gases, at the respirator. A further requisite of such masks is the washout of gas from the mask to ensure that carbon dioxide build up does not occur over the range of flow rates. In the typical flow rates in CPAP treatment, usually between 4 cm H₂₀ and 20 cm H₂₀, prior art attempts at such vents have resulted in excessive noise causing irritation to the user and any bed partners.

Various approaches have been developed in the prior art to attempt to reduce the noise when CPAP therapy is provided. For example, in PCT Patent Application No. WO98/34665 it has been proposed that the vent include a resilient plug with rounded edge apertures to reproduce noise. However, this is not entirely effective in eliminating the extra noise created by a vent at the mask.

In common with all attempts to improve the fit, sealing and user comfort is the need to avoid a concentrated flow of air at any portion of the respiratory tracts. In particular with oral masks or mouthpieces it is a disadvantage of prior art devices that the oral cavity may become overly dehydrated by use of the device, causing irritation and possible later complications.

SUMMARY OF THE INVENTION

It is an object of the present invention to attempt to provide a patient interface which goes some way to overcoming the abovementioned disadvantages in the prior art or which will at least provide the industry with a useful choice.

Accordingly, in a first aspect the present invention consists in a device for delivering a supply of gases to a patient comprising or including:

a patient interface fittable to said patient's nose or mouth, which in use is in fluid communication with said supply of gases,

connecting member having two ends and interface means, one end of said two ends being locatable within said patient interface and the other end of said two ends is connectable to said supply of gases, said member capable of being fixed into one of two positions, a first position where said member is freely rotatable within said patient interface, and a second position where said interference means prevents the free rotation of said member within said patient interface.

In a second aspect the present invention consists in a continuous positive airways pressure system for delivering gases to a patient comprising or including a pressurised source of gases, transport means, in fluid communication with said pressurised source, adapted to convey said gases, and a nasal mask in fluid communication with said transport means, in use, delivering said gases to said user, said nasal mask comprising or including:

a body portion having an inlet, connected to said transportation means by a connecting member,

sealing means engaged with said body portion, and adapted to seal against the facial contours of said patient, and

securement means attached to or around the head of said user,

wherein said connecting member has two ends and interference means, one end being locatable within said patient interface and the other end of said two ends connectable to said transportation means, said connecting member capable of being fixed into one of two positions, a first position where said member is rotatable within said patient interface, and a second position where said interference means prevents the free rotation of said member within said patient interface.

In a third aspect the present invention consists in a device for delivering a supply of gases to a patient comprising:

a patient interface, which in use is in fluid communication with said supply of gases,

connecting member that connects said patient interface with said supply of gases,

outlet means associated with said connecting member, said outlet means including at least one outlet vent and a funnel, which in use directs and passes a substantial portion gases expired from said patient through said at least one outlet vent.

To those skilled in the art to which the invention relates, many changes in construction and widely differing embodiments and applications of the invention will suggest themselves without departing from the scope of the invention as defined in the appended claims. The disclosures and the descriptions herein are purely illustrative and are not intended to be in any sense limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

One preferred form of the present invention will now be described with reference to the accompanying drawings in which:

FIG. 1 is a block diagram of a humidified positive pressure ventilation system as might be used in conjunction with the present invention,

FIG. 2 is an illustration of the nasal mask in use according to the preferred embodiment of the present invention,

FIG. 3 is a side elevation view of an example of a connector used with a breathing circuit,

FIG. 4 is a perspective view from above of a mouthpiece that may be used with the elbow connector of the present invention,

FIG. 5 is a perspective view from one side and from an inward direction of the mouthpiece of FIG. 4,

FIG. 6 is a cross-section of the mouthpiece of FIG. 4,

FIG. 7 is a cross-sectional view of the mouthpiece of FIG. 4 and a user with the mouthpiece in place to demonstrate the location and positioning thereof in relation to the main features of the patient's anatomy,

FIG. 8 is a perspective view of the mouthpiece with an outer flap in place,

FIG. 9 is a perspective view of the outer flap bent back,

FIG. 10 is a cutaway view of the mouthpiece with the outer flap in use,

FIG. 11 is a perspective view of the outer flap including the ventilation apertures and moisture barrier,

FIG. 12 is a front view of a nasal mask, including a swiveled elbow connection of the present invention,

FIG. 13 is a side view of the swiveled elbow connection as attached to the mask body of the present invention in a first position,

FIG. 14 is an exploded side view of the locking mechanism part of the swiveled elbow connection in the first position,

FIG. 15 is a side view of the swiveled elbow connection as attached to the mask body of the present invention, in a second position,

FIG. 16 is an exploded side view of the locking mechanism part of the swiveled elbow connection in the second position,

FIG. 17 shows a nasal mask body and elbow connector with diffuser,

FIG. 18 shows a cutaway side view of the bias How director of the present invention, and

FIG. 19 shows a cutaway perspective view of the bias flow director of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides improvements in the delivery of positive pressure ventilation therapy. In particular a patient interface is described which is quieter for the user to wear and reduces the side leakage as compared with the prior art. The patient interface of the present invention includes improvements to the swivel elbow connector, bias flow directional funnel and/or elbow diffuser. It will be appreciated that the patient interface as described in the preferred embodiment of the present invention can be used in respiratory care generally or with a ventilator but will now be described below with reference to use in a humidified positive pressure ventilation system. It will also be appreciated that the present invention can be applied to any form of patient interface including, but not limited to, nasal masks, oral masks and mouthpieces.

With reference to FIG. 1 a humidified positive pressure ventilation system is shown in which a patient 1 is receiving humidified and pressurised gases through a patient interface 2 connected to a humidified gases transportation pathway or inspiratory conduit 3. It should be understood that delivery systems could also be YPAP (Variable Positive Airway Pressure) and BiPAP (Hi-level Positive Airway Pressure) or numerous other forms of respiratory therapy. Inspiratory conduit 3 is connected to the outlet 4 of a humidification chamber 5, which contains a volume of water 6. Inspiratory conduit 3 may contain heating means or heater wires (not shown), which heat the walls of the conduit to reduce condensation of humidified gases within the conduit. Humidification chamber 6 is preferably formed from a plastics material and may have a highly heat conductive base (for example an aluminium base) which is in direct contact with a heater plate 7 of humidifier 8. Humidifier 8 is provided with control means or electronic controller 9 which may comprise a microprocessor based controller executing computer software commands stored in associated memory.

Controller 9 receives input from sources such as user input means or dial 10 through which a user of the device may, for example, set a predetermined required value (reset value) of humidity or temperature of the gases supplied to patient 1. The controller may also receive input from other sources, for example temperature and/or flow velocity sensors 11 and 12 through connector 13 and heater plate temperature sensor 14. In response to the user set humidity or temperature value input via dial 10 and the other inputs, controller 9 determines when (or to what level) to energise heater plate 7 to heat the water 6 within humidification chamber 5. As the volume of water 6 within humidification chamber 5 is heated, water vapour begins to fill the volume of the chamber above the water's surface and is passed out of the humidification chamber 5 outlet 4 with the flow of gases (for example air) provided from a gases supply means or blower 15 which enters the chamber through inlet 16. Exhaled gases from the patient's mouth are passed directly to ambient surroundings.

Blower 15 is provided with variable pressure regulating means or variable speed fan 21, which draws air or other gases through blower inlet 17. The speed of variable speed fan 21 is controlled by electronic controller 18 (or alternatively the function of controller 18 could be carried out by controller 9) in response to inputs from controller 9 and a user set predetermined required value (preset value) of pressure or fan speed via dial 19.

Nasal Mask

A nasal mask that nay be used with the improvements to the swivel elbow connector, bias flow directional funnel and/or elbow diffuser of the present invention is shown in FIG. 2. The mask includes a hollow body 102 with an inlet 103 connected to the inspiratory conduit 3. The mask 2 is positioned around the nose of the user 1 with the headgear 108 secured around the back of the head of the patient 1. The restraining force from the headgear 108 on the hollow body 102 and the forehead rest 106 ensures enough compressive force on the mask cushion 104, to provide an effective seal against the patient's face.

The hollow body 102 is constructed of a relatively inflexible material, for example, polycarbonate plastic. Such a material would provide the requisite rigidity as well as being transparent and a relatively good insulator.

The improved swivel elbow connector, bias flow directional funnel and/or elbow diffuser of the present invention may also be used with a mouthpiece as described below, or with a full facial mask.

Mouthpiece

Referring to FIGS. 3 to 10 a mouthpiece that may utilise the improvements to the swivel elbow connector, bias flow directional funnel and/or elbow diffuser. In this embodiment, the mouthpiece 50 includes a vestibular shield 49 being a generally flat and generally rectangularly-shaped member in front elevation having a curved profile that reflects the curvature of a patient's jaw and in turn the curvature of the labial vestibule region A gases passageway extends through the vestibular shield from an inlet 51 to an outlet 52 in much the same way as with the earlier embodiments. The inlet 51 is provided by a flattened oval-shaped connector 53. The outlet 52 has an even more laterally extended flattened oval shape 54. Most prominently, the mouthpiece 50 includes a tongue depressor 55 extending from the inner face of the vestibular shield 49. The operation of the tongue depressor will be described further on with reference to FIG. 5. The tongue depressor includes a vertical stiffening flange 56 centrally located on its upper surface and extending from the gases outlet 52. In use gases flow easily around the stiffening flange 56 effectively bifurcating the gases outlet 52. The tongue depressor 55 further includes a pair of vertically extending spacers 57, which in use may abut against the roof of the patient's mouth and ensure that the tongue cannot completely block the air passageway. In the mouthpiece 50 the scaling effect of the vestibular shield 49 against the lips of the user is enhanced by providing teeth abutments of significantly increased thickness than the raised area 20 of the earlier embodiments. In particular, an upper teeth abutment 58 and a lower teeth abutment 59 are provided, with the lower teeth abutment 59 protruding further from the inner face of the vestibular shield 49 than the upper teeth abutment 58. This difference serves to match the typical over-bite of most users. The abutments 58 and 59 are not required to be wider than the gases outlet 52.

A notch 60 is provided centrally in the upper edge of the vestibular shield 49 to accommodate the upper frenal attachment. A slight bead 61 is provided around the edge of the vestibular shield 49 for user comfort, with the vestibular shield 49 otherwise being very thin for additional suppleness.

Referring particularly to FIG. 6, the mouthpiece 50 is preferably formed by over-moulding a soft and supple material part 70 over a stiffer material part 67. These can generally be termed the shield part and the passageway-forming insert. The passageway-forming insert preferably includes a pair of upper and lower vertical flanges 63 and 64 to fully engage within the supple material. The passageway-forming insert 67 includes the vertically extending stiffening flange 56 of the tongue depressor 55, together with a curved planar portion 71 forming the backbone of the tongue depressor 55. The vertically extending spacers 57 are of the soft and supple material and arc part of the over-moulding 70, as are the upper and lower teeth abutments 58 and 59.

Referring now to FIG. 7, use of the mouthpiece according to FIGS. 4 to 6 is depicted. With the present mouthpiece 50, the upper and lower lips 85, 86 are further distended by the abutment action of the abutments 75, 76 against the upper and lower teeth 87, 88 respectively, thus forming a seal of greater pressure between the lips 85, 86 and the upper and lower portions respectively of the vestibular shield 49. A lower face 77 of the tongue depressor 55 impinges if necessary on the upper surface 72 of the tongue 85 and retains the tongue in the lower portion of the mouth. This ensures a clear gases outlet 52 from the gases passageway through the vestibular shield. The vertically extending spacers 57, if forced by pressure from the tongue, will engage against the roof of the patient's mouth and maintain a clear air passageway. This stops the sleeping patient unconsciously blocking the oral passageway and reverting to nasal breathing.

Referring now to FIG. 8 of the present invention is illustrated including an extra-oral sealing flap 110. The flap 110 in its natural bias is tapered, the wide-open end of which is shaped to conform to the facial contours around the outside of the mouth of a user. The narrow end joins to a cylindrical section, which is designed to slide over the inlet port 114 of the mouthpiece 112. While this is one method of attachment the flap 100 might also be constructed as an integral part of the mouthpiece 112. The flap 110 needs to be constructed of flexible material. Therefore, materials such as silicone rubber can be employed to fashion the flap.

The outer flap 110 is seen in FIG. 9, in a bent back position. It will be appreciated that when the mouthpiece 112 is being inserted into the mouth of a users the outer flap 110 is intended to be in this bent back position to aid insertion. Prior to insertion, the outer flap is bent back by simply pressing on its outer periphery 116, until it snaps into the bent back position, in which it will stay unaided.

In FIG. 10 we see the outer flap 110 in use with the mouthpiece 112 in the mouth 117 of a user 120. Once correctly positioned in the mouth 116, the outer flap 110 may be adjusted into its operational position by pressing on its outer periphery 116 until it snaps back to press against the outside of the mouth 118. Due to the relative position of the vestibular shield 122 and the outer flap 110, the outer flap 110 is unable to fully reach its natural bias and thereby inflicts a compressive force on the outside of the mouth 118.

It will be appreciated that as well as providing a substantially airtight seal the addition of the outer flap provides enough compressive force on the mouth to keep the mouthpiece and conduit in place without the need for straps. This allows the administering of positive airway pressure ventilation therapy to be considerably less obtrusive than traditional methods.

In a further additional improvement shown in FIG. 11, the outer flap 300 is shown in perspective. Included are ventilation apertures 302, 303 either side of the gases port 304, which arc surrounded by a ridge 306 acting as a moisture barrier. The apertures 302, 303 are provided such that any excess moisture leaking from the mouth will migrate to the apertures where they may evaporate. Small vents in the conduit may be used to direct small amounts of pressurised gas at the apertures to aid evaporation. The ridge 306 is included to ensure that no moisture migrates further into the scaling region 308, as this would be detrimental to the sealing properties of the flap.

Interface Connection

Attention is now directed to FIG. 3. It has been found that an additional factor in the effectiveness of any patient interface 2, is the manner in which the interface is connected to the breathing circuit. The weight of the breathing circuit, and any attempted movement of one other of the breathing circuit and the interface 2 relative to the other, is one of the largest influences tending to dislodge the interface 2. It must be noted that the interface 2 must remain in position and maintain a seal during all sleep, when the user has no muscle tone.

The connection is usually provided between a breathing circuit and an interface 2, which decouples the interface 2 from the breathing circuit. This type of configuration is shown in FIG. 3, where the interface is a mouthpiece, although a nasal mask may be used in place of the mouthpiece. The connection 40 is effective in reducing the forces placed on the interface 2 by the breathing circuit 41 when the user moves around during sleep.

To connect between the gases outlet 42, which is vertical when the user is lying on his or her back, and the breathing circuit 41, which is generally horizontal, a L-shaped elbow connector 45 is incorporated in the connection 40. The elbow connector 45 may be incorporated in the interface 2. The elbow connector 45 is formed at a right angle and provides a positive pressure on the interface 2. The elbow connector 45 may include a swivel joint and may be disconnected from gaseous outlet 42. The connection 40 further includes a connecting tube 46 provided between the elbow 45 and the breathing circuit 41. The connecting tube 46 is preferably connected to the breathing circuit 41 by a swivel joint 48 for reasons described herein. The breathing circuit 41, while flexible, will necessarily be stiff enough to maintain its inter over comparatively long turns, while the flexible connecting tube 46, being only a short length, for example 10 centimeters, merely has to span between the patient's mouth and chest, and can thereby be made in a manner that would not be suitable for long runs. Furthermore, as a result of the short length of the connecting tube 46, the connecting tube 46 does not need to incorporate significant insulation or heating capability. The connecting tube 46 may be formed from a thin plastic membrane supported over helical or double helical or corrugated supporting ribs. In such a case, the support makes the connection tube 46 laterally flexible and resistant to torsion. The elbow swivel connector 45 allows for movement of the connection tube 46 relative to the interface 2. The swivel connector 48 allows for movement of the connection tube 46 relative to the breathing circuit 41. It is to be understood that one or both of the swivel joints 45, 48 could be eliminated, but the preferred embodiment includes elbow swivel connector 48.

Fixable Swivel Joint

The nasal mask or mouthpiece as described above can be provided with an improved L-shaped elbow connector similar to that described above. Referring to FIGS. 12 to 16 a L-shaped elbow 401 is fixed to the mask base 402 on the nasal mask although not shown in the Figures to inlet 51 of the mouthpiece 50. Hereinafter when reference is made to “mask body” or “mask base 402” it is intended to refer to either the mask body or inlet 51 of the mouthpiece. A portion 403 of the elbow connector can be rotated about a point X in the directions of arrows A and B. The elbow connector 401 is connectable at its end 404 to the breathing circuit or conduit 3 as described with reference to FIGS. 1 and 2. The connector 401 is designed to be fixed into one of two positions and is able to be fully removed from the mask base 402. If the connector 401 is assembled in a first position, it is able to freely swivel, as indicated by the arrows labeled A and B on FIG. 12. If the elbow is pushed into a second position, an area of interference prevents the connector from freely swiveling.

Attention is now drawn to FIGS. 13 and 14 where the mask body 501 and elbow connector 502 are shown in a first position where the connector 502 is able to freely rotate 360 degrees about a vertical axis out of the mask body. The connector 502 is connected to an aperture in the centre of the mask body, so that in use, gases flow from the breathing circuit through the elbow connector and aperture in the mask body and into the patient's lungs. The elbow connector 502 is held within the aperture in the mask body 501 by way of tubular connector 503 located on the arm of the elbow connector 502. The tubular connector 503 comprises various ridges and protrusions, moulded in the external surface of the elbow connector's arm, that meet with complimentary ridges and protrusions moulded in the interior surface of the aperture in the mask body (or the inlet 51 itself).

In particular, referring to FIG. 14, when the connector 502 is in the position as shown in FIG. 13, the ridge 601 and protrusion 602 in the connector 502 act with the small ridge 603 and protrusion 604 in the interior surface of the mask body, to lock the elbow connector 502 into a position that enables the elbow to swivel freely within the mask body. To remove the elbow 502 from the mask body 501 a force in the direction of arrow C (see FIG. 13) must be placed on the elbow so that the protrusion 602 on the elbow is forced past the protrusion 604 on the mask body, thereby releasing the connector 502 from the mask body.

The elbow connector may be pushed downwards to into the mask body to a position as shown in FIGS. 15 and 16. Here, the protrusion 602 of the elbow has been pushed past the lower protrusion 802 on the mask body 501 and sits within a complimentary ridge 801 in the mask. The protrusion 604 on the mask abuts the ridge 601 on the elbow connector and the exterior side surface 804 of the elbow connector above the ridge 601 abuts the interior surface 805 of the mask aperture. The area of interference 803 between these surfaces prevents the elbow from freely swiveling within the mask.

The improvements, as described above, to the elbow connector of the present invention provides an attachment that can either freely rotate, or be locked in a particular position according to the patient's desires. The improvement to the prior art swivel connectors is that the short flexible tubing (46 as described with reference to FIG. 3) is no longer required.

Flow Diffuser and Bias Flow Directional Funnel

In an alternative form of the present invention, and in order to reduce the noise caused by expiratory gases being expelled from the mask or mouthpiece, either may be provided with an elbow connector having a diffuser. In prior art systems the flow diffuser is usually provided within the elbow connector at the point of connection to the mask body or inlet to the mouthpiece, in the present invention it is envisaged to provide a diffuser on the elbow connector. The following description refers to nasal mask when describing the diffuser. The diffuser may also be provided with an elbow connector used with a mouthpiece as previously described.

FIG. 17 shows a nasal mask 901 and elbow connector 902 as that has a diffuser located along the length of the connector 902 previously. The elbow connector 902 includes a diffuser 903 on its exterior surface, the diffuser is a duct that provides for the broadening of the airflow and reduction in the airflow speed. In the preferred form the duct has outlet vent holes 904, 905 and the duct is made out of flexible rubber material. Note must be made that any number of vent holes may be provided in the duct, the preferred form shown in FIG. 17, merely shows two vents. The duct is preferably provided with a bias flow directional funnel, which will be described below.

Referring to FIGS. 18 and 19, during positive pressure ventilation treatment a portion of the inlet air flow breathed by the patient is exhausted directly through the bias holes 1001, 1002. The only venting required is to clear the expired CO₂ gas from within the elbow connector 902. Therefore a funnel 1004 is provided within the elbow connector 902 that directs the exhaled CO₂ gases to the bias holes 1001, 1002 but does not direct the inlet airflow from the ventilation machine out the bias holes.

The purpose of the funnel is to vent exhaled air from the breathing system to remove CO₂ gases. With the prior art breathing systems it has been found that there is continuous leaking of gases through the vent holes during inspiration and expiration by the patient. Therefore, a loss of pressure occurs due to escaping air. Thus, on inspiration the patient receives less pressure and thus less breathing therapy, and therefore this requires that vent holes are provided that are as small as possible to lessen this effect.

During expiration by the patient it is preferred that most of the exhaled gases are vented through the vent holes, in order to prevent pressure spikes and to ensure CO₂ gases are expelled from the breathing tubing. The funnel therefore provides for shielding of the vent holes during inspiration, but enhances the venting of CO₂ gases by providing directional flows during expiration, this also allows for vent holes to be increased in size, providing larger exhaust areas.

Inlet airflow E flows from the ventilating system through the elbow connector 902 in the direction of arrows F, G and H and into the patient's lungs. The air that is exhaled, as indicated by arrow I, flows through the funnel 1004 that has been moulded within the interior of the elbow connector 902. The funnel 1004 is tubular in shape and provides for the funneling of the exhausted CO₂ gases through the outlet bias holes 1001, 1002. In use, the elbow connector 902 takes the place of elbow connector 45 which is shown in FIG. 3. Therefore, in use, the funnel 1004 is located in and extends along the portion of the elbow connector 902 which is substantially vertical when the patient is lying on his or her back wearing the patient interface 2.

Providing such a diffuser on the elbow connector effectively minimises the noise generated by the outward flow of expiratory gases from the mask. The diffuser of the present invention requires little or no maintenance and improves user comfort. The providing of a directional funnel within the elbow connector further minimises noise and reduces pressure spikes during exhalation. 

What is claimed is:
 1. A patient interface comprising: a mask assembly configured to be coupled with an elbow assembly for delivering a pressurized gas to a patient; the elbow assembly comprising: a first leg configured to connect to a source of the pressurized gas at a first end of the elbow assembly; and a second leg configured to swivelably connect to the mask assembly, the second leg comprising: a second end of the elbow assembly configured to insertably interface with the mask assembly; an outer conduit and an inner conduit fixed within the outer conduit, a first tubular section of the outer conduit disposed radially outward of a second tubular section of the inner conduit, the inner conduit and the outer conduit extending towards the second end of the elbow assembly from a front wall of the outer conduit, a distal end of the outer conduit disposed beyond a distal portion of the second tubular section of the inner conduit in an axial direction such that the distal portion of the second tubular section is disposed within a straight section of the second leg; a first flow path defined between the inner conduit and the outer conduit, the first flow path accommodating a first flow of gases in a first direction; a second flow path defined within the inner conduit, the second flow path accommodating a second flow of gases in a second direction, the first direction being directly opposite the second direction in at least a portion of the second leg; and a diffuser comprising a plurality of exhaust vents in the front wall of the outer conduit.
 2. The patient interface of claim 1, wherein the plurality of exhaust vents are positioned on a curved surface of the front wall.
 3. The patient interface of claim 2, wherein the second leg further comprises at least one protrusion configured to releasably engage a channel on the mask assembly.
 4. The patient interface of claim 3, wherein the diffuser is at an opposite end of the second leg from the second end of the elbow assembly.
 5. The patient interface of claim 4, wherein the first leg is configured to swivelably connect with the source of the pressurized gas.
 6. The patient interface of claim 5, wherein the second tubular section of the inner conduit is configured to shield the diffuser from an inspiratory gas from the source of the pressurized gas.
 7. The patient interface of claim 6, wherein an end of the inner conduit is fixed with the front wall adjacent to the diffuser and the distal portion of the inner conduit extends towards the second end of the elbow assembly from the front wall.
 8. The patient interface of claim 7, wherein the second flow of gas comprises an expiratory gas from the mask assembly.
 9. The patient interface of claim 8, wherein the first flow of gas comprises an inspiratory gas from the source of the pressurized gas.
 10. The patient interface of claim 1, wherein a distal end of the inner conduit includes the distal portion, the distal portion being a circumferential end portion of the second tubular section.
 11. The patient interface of claim 10, wherein the distal end of the inner conduit is offset from the second end of the elbow assembly towards the first leg of the elbow assembly in the axial direction.
 12. A patient interface comprising: a mask assembly configured to be coupled with an elbow assembly for delivering a pressurized gas to a patient; the elbow assembly comprising: a first leg configured to connect to a source of the pressurized gas at a first end of the elbow assembly; and a second leg configured to swivelably connect to the mask assembly, the second leg comprising: a second end of the elbow assembly configured to insertably interface with the mask assembly; an outer conduit and an inner conduit fixed within the outer conduit, a first tubular section of the outer conduit disposed radially outward of a second tubular section of the inner conduit, the inner conduit extending towards the second end of the elbow assembly from a front wall of the outer conduit, a distal portion of the second tubular section disposed within a straight section of the second leg; a first flow path defined between the inner conduit and the outer conduit, the first flow path accommodating a first flow of gases in a first direction; a second flow path defined within the inner conduit, the second flow path accommodating a second flow of gases in a second direction, the first direction being directly opposite the second direction in at least a portion of the second leg; and a diffuser comprising a plurality of exhaust vents in the front wall of the outer conduit; wherein the first tubular section of the outer conduit has a first length and the second tubular section of the inner conduit has a second length, the first length being greater than the second length.
 13. A patient interface comprising: a mask assembly configured to be coupled with an elbow assembly for delivering a pressurized gas to a patient; the elbow assembly comprising: a first portion configured to connect to a source of the pressurized gas at a first end of the elbow assembly; and a second portion configured to swivelably connect to the mask assembly, the second portion comprising a second end of the elbow assembly, an outer wall of the second portion having a plurality of exhaust vent holes extending therethrough, a portion of the outer wall configured to be insertable within the mask assembly, and an inner tubular wall fixed within a tubular portion of the outer wall, the inner tubular wall formed as an integral unit with the outer wall such that both the inner tubular wall and the outer wall swivel with respect to the mask assembly, a circumferential end portion of the inner tubular wall extending within the tubular portion of the outer wall in the second portion; wherein the inner tubular wall extends towards the second end of the elbow assembly from adjacent the plurality of exhaust vents and the inner tubular wall shields the plurality of exhaust vent holes from an inspiratory gas flow from the source of the pressurized gas; and wherein an end of the outer wall is offset in an axial direction away from the plurality of exhaust vents from the circumferential end portion of the inner tubular wall.
 14. The patient interface of claim 13, wherein the plurality of exhaust vent holes are positioned on a curved surface of the outer wall.
 15. The patient interface of claim 14, wherein the second portion comprises a swivel connector configured to swivelably engage the mask assembly.
 16. The patient interface of claim 15, wherein the swivel connector further comprises at least one protrusion configured to releasably engage a channel on the mask assembly.
 17. The patient interface of claim 16, wherein the plurality of vent holes are at an opposite end of the second portion from the second end of the elbow assembly.
 18. The patient interface of claim 17, wherein the second portion comprises a first flow path from the second end to the plurality of vent holes for exhausting an expiratory gas flow from the mask assembly.
 19. The patient interface of claim 18, wherein the second portion comprises a second flow path from the first end of the elbow assembly to the second end of the elbow assembly for delivering the inspiratory gas flow to the mask assembly.
 20. The patient interface of claim 19, wherein the elbow assembly is configured such that, in use, a direction of fluid flow within the first flow path is directly opposite a direction of fluid flow within at least a portion of the second flow path.
 21. The patient interface of claim 20, wherein the inner tubular wall at least partially defines the first flow path and the second flow path is at least partially defined between the tubular portion of the outer wall and the inner tubular wall. 